The present invention relates to interlocking vinyl siding panels, and to a method of forming the vinyl siding panels. It relates particularly to post formed vinyl siding panels which can be engaged with each other in a positive, snap-type interlock when they are applied to a builing.
Vinyl siding panels are widely used for protecting the exterior walls of buildings, as well as for enhancing the exterior appearance of buildings. The siding panels may have different profiles and exterior finishes, to provide variety in the exterior appearance they can provide to a building. Typically, the siding panels are nailed or otherwise secured to the building to fix them in place.
Formerly, in constructing vinyl siding panels, it was customary to extrude a sheet of vinyl with the entire profile formed therein, and to then cut the sheet of vinyl into panels of appropriate lengths. However, in recent years the vinyl siding industry has been converting from extruded vinyl siding to what is known as "post formed" vinyl siding. Post formed vinyl siding is formed by initially extruding a flat sheet of vinyl, and then forming the sheet of vinyl against or through a die and into its final profile while the vinyl is still in a hot, semi-viscous state. Post forming the vinyl produces a siding with (i) larger radii at the bends and folds than 100% extruded siding, and (ii) more resilience than 100% extruded siding. Thus, post formed siding is generally more damage resistant than 100 percent extruded vinyl siding, i.e. post formed siding does not crack as easily during installation, thermal cycling, impact, etc.
However, in changing from extruded vinyl siding to post formed vinyl siding one problem that has been encountered is the difficulty of providing a positive interlock between adjacent siding panels. The ability to positively interlock a pair of adjacent siding panels is important to the construction industry, because it simplifies the application of the siding panels to a building. Specifically, once one panel has been nailed to a building a subsequent panel can be attached to the building by a single installer, by relying on the interlock to hold the entire length of the panel in place while the installer nails it in place. If a positive interlock is not achieved, two installers are generally necessary to apply each panel to the building. It has been found that with post formed vinyl siding it is difficult to provide the siding panels a good interlocking siding profile. Many post formed vinyl siding panels rely on a friction fit to interlock with each other. However, due to difficulties in maintaining dimensional tolerances, vinyl panels that rely on a friction fit are often subject to slippage. This makes the application of the panels to a building cumbersome, because two installers are necessary to apply each panel to the building.